/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http.impl.io;

import java.io.IOException;
import java.util.Iterator;

import org.apache.http.Header;
import org.apache.http.HttpException;
import org.apache.http.HttpMessage;
import org.apache.http.io.HttpMessageWriter;
import org.apache.http.io.SessionOutputBuffer;
import org.apache.http.message.BasicLineFormatter;
import org.apache.http.message.LineFormatter;
import org.apache.http.params.HttpParams;
import org.apache.http.util.CharArrayBuffer;

/**
 * Abstract base class for HTTP message writers that serialize output to an
 * instance of {@link SessionOutputBuffer}.
 * 
 * @since 4.0
 */
public abstract class AbstractMessageWriter implements HttpMessageWriter {

	protected final SessionOutputBuffer sessionBuffer;
	protected final CharArrayBuffer lineBuf;
	protected final LineFormatter lineFormatter;

	/**
	 * Creates an instance of AbstractMessageWriter.
	 * 
	 * @param buffer
	 *            the session output buffer.
	 * @param formatter
	 *            the line formatter.
	 * @param params
	 *            HTTP parameters.
	 */
	public AbstractMessageWriter(final SessionOutputBuffer buffer,
			final LineFormatter formatter, final HttpParams params) {
		super();
		if (buffer == null) {
			throw new IllegalArgumentException(
					"Session input buffer may not be null");
		}
		this.sessionBuffer = buffer;
		this.lineBuf = new CharArrayBuffer(128);
		this.lineFormatter = (formatter != null) ? formatter
				: BasicLineFormatter.DEFAULT;
	}

	/**
	 * Subclasses must override this method to write out the first header line
	 * based on the {@link HttpMessage} passed as a parameter.
	 * 
	 * @param message
	 *            the message whose first line is to be written out.
	 * @throws IOException
	 *             in case of an I/O error.
	 */
	protected abstract void writeHeadLine(HttpMessage message)
			throws IOException;

	@Override
	public void write(final HttpMessage message) throws IOException,
			HttpException {
		if (message == null) {
			throw new IllegalArgumentException("HTTP message may not be null");
		}
		writeHeadLine(message);
		for (@SuppressWarnings("rawtypes")
		Iterator it = message.headerIterator(); it.hasNext();) {
			Header header = (Header) it.next();
			this.sessionBuffer.writeLine(lineFormatter.formatHeader(
					this.lineBuf, header));
		}
		this.lineBuf.clear();
		this.sessionBuffer.writeLine(this.lineBuf);
	}

}
